The present invention relates to fuel compositions comprising a dispersant additive for hydrocarbon fuels, such as gasoline and diesel fuel, wherein said dispersant additive is the reaction product of i) a hydroxyl-group containing compound; ii) an amine-group containing compound, wherein component ii) is different from component i); and iii) a hydrocarbyl-substituted succinic acylating agent.
It has long been desired to maximize fuel economy and power in diesel engines while enhancing acceleration and preventing knocking and hesitation. Diesel fuel must ignite spontaneously and quickly (within 1 to 2 milliseconds) without a spark. The time lag between the initiation of injection and the initiation of combustion is called ignition delay. In high-speed diesel engines, a fuel with a long ignition delay tends to produce rough operation and knocking.
Two major factors affect ignition delay: the mechanical conditions in the engine and the chemistry of the fuel. The mechanical component is influenced by such factors as compression ratio, motion of the air charge during ignition and ability of the fuel injector to atomize fuel. The chemical component of ignition delay is influenced by such factors as the fuel""s autoignition temperature, specific heat, density, viscosity, and other properties. The ability of a diesel fuel to ignite quickly after injection into a cylinder is known as its cetane number.
To minimize ignition delay in a diesel engine, it is desirable to enhance the mechanical component by maintaining the fuel injector""s ability to precisely atomize fuel by keeping the injectors clean. However, this must be done in such a way that does not negatively affect the chemical component.
It would be beneficial to provide dispersant compositions that are highly effective in minimizing injector deposits in diesel engines, as well as intake valve deposits in gasoline engines, and that provide such an advantage without harm to the engine and without deterioration in engine performance.
Accordingly, one of the objects of the present invention is to provide a diesel fuel that provides effective detergency without attendant deterioration in engine performance.
Problems associated with fuel lubricity arose in the mid-1960""s when a number of aviation fuel pump failures occurred. After considerable research, it was realized that advances in the refining of aviation turbine fuel had resulted in the almost complete removal of the naturally occurring lubricating components from the fuel. The removal of these natural lubricants resulted in the seizure of fuel pump parts. By the mid-1980""s, it seemed likely that a similar problem was imminent in diesel fuel pumps. Fuel injection pump pressures had been steadily increasing while there was also a growing concern to reduce the sulfur content of the diesel fuel. The desire to reduce the sulfur content of the diesel fuel, in an effort to reduce pollution, required the use of more rigorous fuel refining processes. It was determined that as refining processes became more stringent, the naturally occurring sulfur, nitrogen and oxygen containing compounds and polyaromatics which contribute to diesel fuel""s inherent lubricity were reduced or eliminated. In response to these developments, a number of effective lubricity additives were developed for diesel fuels. These additives are now widely used to enhance the lubricity of highly refined, low sulfur diesel fuels.
In certain types of in-line diesel injection pumps, engine oil contacts diesel fuel. Engine oil may also come into contact with the diesel fuel through direct addition of used engine oil to the fuel. Certain types of lubricity additives used in low sulfur diesel fuel have been found to contribute to fuel filter blockage and to pump plunger sticking. Lubricity additives having poor compatibility with engine oil have been shown to cause these problems. Compatibility is defined as the tendency for the diesel fuel containing the lubricity additive not to form fuel insoluble deposits, gels or heavy sticky residues when in contact with engine oil. These deposits, gels or residues have been shown to cause fuel filter blockage and injection pump sticking. The additives of the present invention are compatible with engine oil.
Gasoline fuels are also becoming subject to compositional constraints, including restrictions on sulfur content, in an effort to reduce pollutants. The principal concern is the effect of sulfur on exhaust catalyst life and performance. The lubricity requirements of gasoline are somewhat lower than for diesel fuel since the majority of gasoline fuel injection systems inject fuel upstream of the inlet valves and thus operate at much lower pressures than diesel fuel pumps. However, as automobile manufacturers desire to have electrically powered fuel pumps within the fuel tanks, failure of the pumps can be expensive to repair. These problems are also likely to increase as injection systems become more sophisticated and the gasoline fuels become more highly refined.
Additional pump wear concerns have arisen with the introduction of vehicles having direct injection gasoline (DIG) engines since the fuel pumps for these vehicles operate at significantly higher pressures than traditional gasoline fuel pumps.
Another area subject to pump wear and failure is the use of submerged fuel pumps in gasoline or diesel fuel storage tanks. It is important to reduce the wear of these submerged pumps due to the difficulty of accessing these pumps for repair and maintenance.
Many commercially available gasoline fuels contain gasoline detergents such as polyisobutylene amine and polyether amine. These compounds are known to have a minor effect on the wear properties of the fuel. A growing number of commercially available gasoline fuels contain oxygenates, such as methyltertiarybutylether (MTBE). These oxygenates are known to increase rates of wear of fuel pump components as they have very high friction coefficients. In light of the desire for more highly refined fuels, lower sulfur content and oxygenation of the fuels, there is presently a need for lubricity improvers for hydrocarbon fuels in order to obtain acceptable fuel pump life. The present invention addresses these problems by adding the novel succinic acid derivative reaction products to the fuel.
While the prior art is replete with numerous treatments for fuels, it does not disclose the addition of the present additives to hydrocarbon fuels or teach their use for providing enhanced detergency and lubricity to said fuels.
The present invention relates to the treatment of a hydrocarbon fuel to substantially reduce the wear occasioned upon fuel pumps used to pump said hydrocarbon fuels and to provide effective detergency to the fuels without attendant deterioration in engine performance. The present invention also relates to the discovery that the addition to a fuel of the reaction products of the present invention will improve detergency and lubricity as compared to a similar fuel that has not been treated with said reaction products.
Thus, there is disclosed a fuel composition comprising a major amount of a hydrocarbon fuel and a minor amount of a fuel-soluble dispersant obtained by reacting i) a hydroxyl-group containing compound; ii) an amine-group containing compound, wherein component ii) is different from component i); and iii) a hydrocarbyl-substituted succinic acylating agent. The dispersant additives are preferably present in the fuel in an amount within the range of from about 1 to about 1000 parts by weight of additive per million parts by weight of fuel (ppm w/w). More preferably, the dispersants are present in the fuel in an amount within the range from about 10 to about 500 ppm w/w, most preferably, from about 30 to about 300 ppm w/w.
There is also disclosed a method for reducing the wear of fuel pumps through which a hydrocarbon fuel is pumped, comprising adding a fuel-soluble additive to said fuel wherein the fuel-soluble additive comprises the above-described dispersant and wherein the dispersant additive is added to the fuel in an amount effective to improve the detergency and lubricity of the fuel, typically, the dispersant additive is present in the fuel composition in an amount of at least 1 ppm w/w.
In view of the problems discussed above, a general aspect of the present invention is to provide a fuel additive that gives improved detergency to the fuel and protects the fuel pump from excessive wear and breakdown. A further aspect of the invention is to provide a fuel additive suitable for addition to a fuel that does not damage the fuel system and does not cause an increase in undesirable combustion products.
The additives of the present invention may be categorized as hydrocarbyl-substituted succinic acid amides and/or succinic acid esters and are fuel-soluble reaction products obtained by the reaction of i) a hydroxyl-group containing compound; ii) an amine- group containing compound, wherein component ii) is different from component i); and iii) a hydrocarbyl-substituted succinic acylating agent.
Reactants suitable for use as component i) of the present invention are hydroxyl-group containing compounds capable of reacting with the hydrocarbyl-substituted succinic acylating agent (component iii) to form a succinic acid ester, a succinic acid amide or mixtures thereof, and which possess at least one pendant hydroxyl group after reaction with component iii). The preferred reactants for use as component i) in the present invention are amino-alcohols containing secondary and/or tertiary amines; alkoxylated amines containing secondary and/or tertiary amines; polyols and mixtures thereof. Examples of suitable amino-alcohols include diethanolamine and triethanolamine; representative alkoxylated amines include ethoxylated and propoxylated amines and polyamines. An example of these amines includes, for example, 2-(methylamino)ethanol. Suitable polyols include glycerol, sorbitol and polyalkylene glycols. Most preferred for use as component i) is diethanolamine.
Reactants suitable for use as component ii) of the present invention are amine-containing compounds capable of reacting with the hydrocarbyl-substituted succinic acylating agent (component iii) to form a hydrocarbyl-substituted succinic acid ester, succinic acid amide or mixtures thereof, and which possess at least one pendant amine group after reaction with component iii). The preferred reactants for use as component ii) in the present invention include, but are not limited to, polyamines containing at least one secondary amine group and optionally at least one tertiary amine group, tertiary amino alcohols containing at least one hydroxy group and at least one tertiary amine, and polyamines containing a primary amine and at least one additional amino group.
Representative polyamines containing at least one secondary amine group and optionally at least one tertiary amine group include N-methyl piperazine, N,N,Nxe2x80x3,Nxe2x80x3-tetraalkyldialkylenetriamines (two terminal tertiary amino groups and one central secondary amino group), N,N,N,xe2x80x2Nxe2x80x3,NNxe2x80x2xe2x80x3-pentaalkyltrialkylenetetramines (one terminal tertiary amino group, two internal tertiary amino groups and one terminal secondary amino group), and like compounds, wherein the alkyl groups are the same or different and typically contain no more than about 12 carbon atoms each, and which preferably contain from 1 to 4 carbon atoms each, and 3,3xe2x80x2-iminobis (N,N-dimethyl propylamine) having the structure HN[(CH2)3N(CH3)2]2.
Representative tertiary amino alcohols containing at least one hydroxy group and at least one tertiary amine include N,N-dimethylethanolamine having the structure HOxe2x80x94C2H4xe2x80x94N(CH3)2.
Representative polyamines containing a primary amine and at least one additional amine group include alkylene polyamines having at least one suitably reactive primary amino group in the molecule. Other substituents may be present in the polyamine. In one embodiment, the alkylene polyamine is a polyethylene polyamine. Suitable alkylene polyamine reactants include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine, octaethylenenonamine, nonaethylenedecamine, decaethyleneundecamine and mixtures of such amines having nitrogen contents corresponding to alkylene polyamines of the formula H2Nxe2x80x94(Axe2x80x94NHxe2x80x94)nH, where A is divalent ethylene or propylene and n is an integer of from 1 to 10. The alkylene polyamines may be obtained by the reaction of ammonia and dihalo alkanes, such as dichloro alkanes. Thus, the alkylene polyamines obtained from the reaction of 2 to 11 moles of ammonia with 1 to 10 moles of dichloro alkanes having 2 to 6 carbon atoms and the chlorines on different carbon atoms are suitable alkylene polyamine reactants.
In another embodiment of the present invention, the amine useful as component ii) is a polyamine having at least one primary amino group and at least one tertiary amino group in the molecule. Examples of suitable polyamines N,N,Nxe2x80x2,Nxe2x80x3-tetraalkyltrialkylenetetramines (one terminal tertiary amino group, two internal tertiary amino groups and one terminal primary amino group), tris(dialkylaminoalkyl)aminoalkylmethanes (three terminal tertiary amino groups and one terminal primary amino group), and like compounds, wherein the alkyl groups are the same or different and typically contain no more than about 12 carbon atoms each, and which preferably contain from 1 to 4 carbon atoms each. Most preferably these alkyl groups are methyl and/or ethyl groups. Suitable polyamine reactants include N, N-dialkyl- alpha, omega-alkylenediamine, such as those having from 3 to about 6 carbon atoms in the alkylene group and from 1 to about 12 carbon atoms in each of the alkyl groups, which most preferably are the same but which can be different. Most preferred is N,N-dimethyl-1,3-propanediamine.
The hydrocarbyl-substituted succinic acylating agents useful in the present invention is a hydrocarbyl-substituted succinic acylating agent in which the hydrocarbyl substituent contains an average of 50 to 100, preferably 64 to 80, carbon atoms.
The hydrocarbyl substituent of the acylating agent is preferably an alkyl or alkenyl group having the requisite number of carbon atoms as specified above. Alkenyl substituents derived from poly-alpha-olefin homopolymers or copolymers of appropriate molecular weight (e.g., propene homopolymers, butene homopolymers, C3 and C4 alpha-olefin copolymers, and the like) are suitable. Most preferably, the substituent is a polyisobutenyl group formed from polyisobutene having a number average molecular weight (as determined by gel permeation chromatography) in the range of 700 to 2100, preferably 800 to 1300, most preferably 900 to 1000. So-called high reactivity polybutylenes having relatively high proportions of polymer molecules having a terminal vinylidene group, formed by methods such as described, for example, in U.S. Pat. No. 4,152,499 and W. German Offenlegungsschrift 29 04 314, are also suitable for use in forming the hydrocarbyl substituted acylating agents of the present invention.
Hydrocarbyl-substituted succinic acid or anhydride acylating agents and methods for their preparation and use in the formation of succinimide are well known to those skilled in the art and are extensively reported in the patent literature. See for example the following U.S. Pat. Nos. 3,018,247; 3,018,250; 3,578,422; 3,658,494; 3,658,495; 3,912,764; 4,110,349 and 4,234,435, among others.
When utilizing the general procedures such as described in these and other patents, the important considerations insofar as the present invention is concerned, are to insure that the hydrocarbyl substituent of the acylating agent contain the requisite number of carbon atoms, that the acylating agent be reacted with the requisite amines and/or alcohols, and that the reactants be employed in proportions such that the resultant reaction products contain the requisite proportions of the chemically combined reactants, all as specified herein. When utilizing this combination of features, dispersants are formed which possess exceptional effectiveness in controlling or reducing the amount of deposits and exhaust emissions formed during engine operation as well as improved lubricity compared to conventional succinimide detergents.
The hydrocarbyl-substituted succinic acylating agents include the hydrocarbyl-substituted succinic acids, the hydrocarbyl-substituted succinic anhydrides, the hydrocarbyl-substituted succinic acid halides (especially the acid fluorides and acid chlorides), and the esters of the hydrocarbyl-substituted succinic acids and lower alcohols (e.g., those containing up to 7 carbon atoms), that is, hydrocarbyl-substituted compounds which can function as carboxylic acylating agents. Of these compounds, the hydrocarbyl-substituted succinic acids and the hydrocarbyl-substituted succinic anhydrides and mixtures of such acids and anhydrides are generally preferred, the hydrocarbyl-substituted succinic anhydrides being particularly preferred.
The acylating agent used in producing the dispersants useful in this invention is preferably made by reacting a polyolefin of appropriate molecular weight (with or without chlorine) with maleic anhydride. However, similar carboxylic reactants can be employed such as maleic acid, fumaric acid, malic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, ethylmaleic anhydride, dimethylmaleic anhydride, ethylmaleic acid, dimethylmaleic acid, hexylmaleic acid, and the like, including the corresponding acid halides and lower aliphatic esters.
The reaction between the amines, or alcohols, i) and ii) and the hydrocarbyl-substituted succinic acylating agent (component iii) is generally conducted at temperatures of 80xc2x0 C. to 200xc2x0 C., more preferably 100xc2x0 C. to 180 xc2x0 C., such that a succinic acid ester and/or a succinic acid amide is formed. These reactions may be conducted in the presence or absence of an ancillary diluent or liquid reaction medium, such as a mineral lubricating oil solvent. Water is evolved and can be removed by azeotropic distillation during the course of the reaction. Suitable solvent oils include natural and synthetic base oils and high boiling hydrocarbon solvents such as toluene or xylene. The natural oils are typically mineral oils. Suitable synthetic diluents include polyesters, hydrogenated or unhydrogenated poly-alpha-olefins (PAO) such as hydrogenated or unhydrogenated 1-decene oligomer, and the like. Blends of mineral oil and synthetic oils are also suitable for this purpose.
The order of reacting components i), ii) and iii) is not particularly critical when component ii) contains only secondary amine groups or only secondary and tertiary amine groups. However, when component ii) contains a primary amine group, care must be taken to avoid forming succinimide groups by reacting the primary amines with all of the available succinic acylating agents thus leaving no available reactive sites for amine i) on the succinic acylating agent. The formation of undesired succinimides may be minimized by first reacting components i) and iii) in their desired proportions prior to the addition of component ii); in another embodiment, small amounts of component ii) containing primary amine groups may be added before or simultaneously with the addition of component i) so long as component ii) is present in an amount so as to provide less than 1 mole of primary amine per 1 mole of succinic acylating agent. Although some succinimide groups may form using this method, some hydrocarbyl-substituted succinic acylating agent capable of reacting with the hydroxyl-group containing component i) would still remain and the benefits of the invention still recognized.
Typically, the dispersant additives of the present invention are formed by reacting a hydrocarbyl-substituted succinic acylating agent (iii), a hydroxyl-group containing compound (i); an amine-group containing compound (ii) in the molar ratios of 1.0:0.2-1.8:0.2-1.8, preferably 1:0.5-1.5:0.5-1.5.
When formulating the fuel compositions of this invention, the dispersant additives (with or without other additives) are employed in an amount effective to improve the detergency of the fuel. Generally speaking the fuels of this invention will contain, on an active ingredient basis, an amount of dispersant additive in the range of about 1 to 1000 parts by weight of additive per million parts by weight of fuel.
An advantage of the present invention is that the additive reaction products do not detrimentally impact the combustion properties of the fuel. Further, the reaction products of the present invention can contribute lubricity benefits to the formulated fuel compositions. The improvements in the fuels lubricity will allow formulation with less, or even no, additional lubricity additive. Further, the improved fuel lubricity can reduce fuel pump wear.
The fuel compositions of the present invention may contain supplemental additives in addition to the reaction products described above. Said supplemental additives include supplemental dispersant/detergents, cetane improvers, octane improvers, antioxidants, carrier fluids, metal deactivators, dyes, markers, corrosion inhibitors, biocides, antistatic additives, drag reducing agents, demulsifiers, dehazers, anti-icing additives, antiknock additives, anti-valve-seat recession additives, lubricity additives and combustion improvers.
Cyclopentadienyl manganese tricarbonyl compounds such as methylcyclopentadienyl manganese tricarbonyl are preferred combustion improvers because of their outstanding ability to reduce tailpipe emissions such as NOx and smog forming precursors and to significantly improve the octane quality of gasolines, both of the conventional variety and of the xe2x80x9creformulatedxe2x80x9d types.
The base fuels used in formulating the fuel compositions of the present invention 20 include any base fuels suitable for use in the operation of spark-ignition or compression-ignition internal combustion engines such as diesel fuel, jet fuel, kerosene, leaded or unleaded motor and aviation gasolines, and so-called reformulated gasolines which typically contain both hydrocarbons of the gasoline boiling range and fuel-soluble oxygenated blending agents, such as alcohols, ethers and other suitable oxygen-containing organic compounds. Oxygenates suitable for use in the present invention include methanol, ethanol, isopropanol, t-butanol, mixed C1 to C5 alcohols, methyl tertiary butyl ether, tertiary amyl methyl ether, ethyl tertiary butyl ether and mixed ethers. Oxygenates, when used, will normally be present in the base fuel in an amount below about 25% by volume, and preferably in an amount that provides an oxygen content in the overall fuel in the range of about 0.5 to about 5 percent by volume.
Any middle-distillate fuel may be used in the present invention, however, high-sulfur content fuels typically do not require additional lubricity additives. In a preferred embodiment, the middle-distillate fuel is a diesel fuel having a sulfur content of up to about 0.2% by weight, more preferably up to about 0.05% by weight, as determined by the test method specified in ASTM D 2622-98.
The additives used in formulating the preferred fuels of the present invention can be blended into the base fuel individually or in various sub-combinations. However, it is preferable to blend all of the components concurrently using an additive concentrate (i.e., additives plus a diluent, such as a hydrocarbon solvent). The use of an additive concentrate takes advantage of the mutual compatibility afforded by the combination of ingredients when in the form of an additive concentrate. Also, the use of a concentrate reduces blending time and lessens the possibility of blending errors.